Performance Enhanced Heat Spreader

ABSTRACT

Embodiments of the present invention include methods of disposing a metallic coating layer comprising a metal in an amorphous and/or fine grain microstructure over at least a portion of a surface of a pyrolytic graphite substrate, the metal comprising Nickel, Iron, a Nickel-Iron Alloy, or any combination thereof, and the grains of the metal being of 1 nm to 10000 nm in size. Embodiments of the invention also encompass the coated pyrolytic graphite articles. The coated substrate exhibits a thermal conductivity not less than the uncoated substrate.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional patentapplication No. 61/884,818, filed on Sep. 30, 2013, which isincorporated herein by reference in its entirety, and expresslyincluding any drawings.

BACKGROUND

The present invention relates to methods of applying a coating to asubstrate of pyrolytic graphite and the coated pyrolytic graphite whichexhibits an improved thermal conductivity. The coated pyrolytic graphitecan be used as a heat spreader for conducting heat from a device.Electronic components are becoming smaller while heat dissipationrequirements are becoming greater. In order to dissipate heat generatedby these electronic components, heat spreaders are utilized between theelectronic component and a heat sink. Heat spreaders can be made of asolid thermally conductive metal. The solid conductive metal has alimited ability to spread heat and has limited thermal conductivitycharacteristics.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference,and as if each said individual publication, patent, or patentapplication was fully set forth, including any figures, herein.

SUMMARY

Non-limiting embodiments of the invention are described in the followinglabeled paragraphs:

Embodiments of the present invention encompass methods of disposing ametallic coating layer comprising a metal over at least a portion of asurface of a pyrolytic graphite substrate, the metal comprising Nickel,Iron, a Nickel-Iron Alloy, or any combination thereof, and the grains ofthe metal being of 1 nanometers (nm) to 10000 nm in size, the metalbeing amorphous, or both.

Embodiments of the present invention encompass articles comprising ametallic coating layer comprising a metal disposed over at least aportion of a surface of a pyrolytic graphite substrate, the metalcomprising Nickel, Iron, a Nickel-Iron Alloy, or any combinationthereof, and the grains of the metal being of 1 nm to 10000 nm in size,the metal being amorphous, or both.

In embodiments of the present invention, such as, but not limited to,the method described in paragraph [0001] or the article described inparagraph [0002], the pyrolytic graphite substrate is highly orientedpyrolytic graphite, chemical vapor deposition deposited pyrolyticgraphite, or a combination thereof.

In embodiments of the present invention, such as, but not limited to,the method described in paragraph [0001] or the article described inparagraph [0002], the pyrolytic graphite substrate is PYROID® HT,PYROID® SN, PYROID® CN, or a combination thereof.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0004], a Nanovate™ N2040 coating disposed over the substratecomprises the metallic coating layer.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0005], the metallic coating layer comprises a fine grained metalof metal grain size from 2 nm to 5000 nm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0006], the metallic coating comprises a fine grained metal ofmetal grain size from 5 nm to 1000 nm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0007], the metallic coating comprises a fine grained metal ofmetal grain size from 10 nm to 500 nm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0005], the metallic coating comprises a fine grained metal of ametal grain size in a range having a minimum size selected from 2 nm, 5nm, and 10 nm, and having a maximum size selected from 100 nm, 500 nm,1000 nm, 5000 nm, and 10,000 nm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0009], the coating comprises an alloying addition.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraph [0010], thealloying addition is selected from the group consisting of B, C, H, O,P, S, and combinations thereof.

In embodiments of the present invention, such as, but not limited to,the methods or articles described in paragraph [0010], the alloyingaddition is selected from the group consisting of Ag, Au, B, Cr, Mo, P,Pb, Pd, Rh, Ru, Sn, Zn, and combinations thereof.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0012], the coating comprises solid particulates where the solidparticulates are metals; metal oxides; carbides of B, Cr, Bi, Si, W, ora combination thereof; carbon; glass; polymer materials; MoS₂, or anycombination thereof.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraph [0013], thepolymer materials are selected from the group consisting ofpolytetrafluoroethylene, polyvinyl chloride, polyethylene,polypropylene, acrylonitrile-butadiene-styrene, epoxy resins, andcombinations thereof.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0014], the coating comprises up to 95% by volume solidparticulates.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0014], the coating comprises 1% to 95% by volume solidparticulates.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0016], the metallic coating layer thickness is 10 μm to 50 mm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraph [0017], themetallic coating layer thickness is 25 μm to 25 mm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraph [0018], themetallic coating layer thickness is 30 μm to 5 mm.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0019], one or more intermediate coating layers are applied tothe substrate before the metallic coating layer is applied.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0020], at least one of the intermediate coating layer(s)comprises a metal, a polymer, or both a metal and a polymer.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0021], the intermediate coating layer thickness is less than themetallic coating layer thickness by at least 20%.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0022], the metallic coating layer, and the intermediate coatinglayer(s), if present, covers all of the exterior surface of thesubstrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0022], the metallic coating layer, and the intermediate coatinglayer(s), if present, covers only a portion of the exterior surface ofthe substrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0024], the thermal conductivity of the coated pyrolytic graphiteis not less than the uncoated pyrolytic graphite substrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0025], the substrate coated with the metallic coating layerexhibits a thermal conductivity of about 105% of the thermalconductivity of the uncoated substrate, or of not less than 105% ofuncoated substrate and also not more than 250% of the uncoatedsubstrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0026], the substrate coated with the metallic coating layerexhibits a thermal conductivity of about 110% of the thermalconductivity of the uncoated substrate, or of not less than 110% ofuncoated substrate and also not more than 250% of the uncoatedsubstrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0027], the substrate coated with the metallic coating layerexhibits a thermal conductivity of about 115% of the thermalconductivity of the uncoated substrate, or of not less than 115% ofuncoated substrate and also not more than 250% of the uncoatedsubstrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0028], the substrate coated with the metallic coating layerexhibits a flexural strength greater than that of the uncoatedsubstrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0029], the substrate coated with the metallic coating layerexhibits a flexural strength of about 110% of the flexural strength ofthe uncoated substrate, or of not less than 110% of the uncoatedsubstrate and also not more than 2000% of the uncoated substrate.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0030], the metallic coating layer has a room temperaturecoefficient of linear thermal expansion in all directions of less than25×10⁻⁶ K⁻¹.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0030], the metallic coating layer has a room temperaturecoefficient of linear thermal expansion in all directions in the rangebetween 5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraphs[0001]-[0032], the substrate is a heat spreader.

In embodiments of the present invention, such as, but not limited to,any one of the methods or articles described in paragraph [0033], theheat spreader is any one of those described in U.S. Pat. Nos. 8,085,531,7,859,848, 7,808,787, and 8,059,408.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of the structure of a graphite sheet.

FIG. 2 shows a manufacturing method of highly oriented pyrolyticgraphite.

DETAILED DESCRIPTION

Use of the singular herein, including the claims, includes the pluraland vice versa unless expressly stated to be otherwise. That is, “a,”“an” and “the” refer to one or more of whatever the word modifies. Forexample, “an article” may refer to one articles, two articles, etc. Bythe same token, words such as, without limitation, “articles” wouldrefer to one article as well as to a plurality of articles unless it isexpressly stated or obvious from the context that such is not intended.

As used herein, words of approximation such as, without limitation,“about,” “substantially,” “essentially,” and “approximately” mean thatthe word or phrase modified by the term need not be exactly that whichis written but may vary from that written description to some extent.The extent to which the description may vary from the literal meaning ofwhat is written, that is the absolute or perfect form, will depend onhow great a change can be instituted and have one of ordinary skill inthe art recognize the modified version as still having the properties,characteristics and capabilities of the modified word or phrase. Ingeneral, but with the preceding discussion in mind, a numerical valueherein that is modified by a word of approximation may vary from thestated value by ±15%, unless expressly stated otherwise.

As used herein, any ranges presented are inclusive of the end-points.For example, “a temperature between 10° C. and 30° C.” or “a temperaturefrom 10° C. to 30° C.” includes 10° C. and 30° C., as well as anytemperature in between.

As used herein, a material that is described as a layer or a film (e.g.,a coating) “disposed over” an indicated substrate refers to, e.g., acoating of the material deposited directly or indirectly over at least aportion of the surface of the substrate. A “layer” or a “coating” of agiven material is a region of that material whose thickness is smallcompared to both its length and width (e.g., the length and widthdimensions may both be at least 5, 10, 20, 50, 100 or more times thethickness dimension in some embodiments). Direct depositing means thatthe coating is applied directly to the surface of the substrate.Indirect depositing means that the coating is applied to an interveninglayer that has been deposited directly or indirectly over the substrate.A coating is supported by a surface of the substrate, whether thecoating is deposited directly, or indirectly, onto the surface of thesubstrate. As used herein a layer need not be planar, for example,taking on the contours of an underlying substrate. Layers can bediscontinuous. A layer may be of non-uniform thickness. The terms“coating”, “layer”, and “coating layer” will be used interchangeably andrefer to a layer, film, or coating as described in this paragraph.

As used herein, the term “coating thickness” or “layer thickness” refersto the depth in a deposit direction.

The invention will now be described in detail by reference to thefollowing specification and non-limiting examples. Without furtherelaboration, it is believed that one skilled in the art can, using thepreceding description, utilize the present invention to its fullestextent. The following embodiments are, therefore, to be construed asmerely illustrative, and not limitative of the remainder of thedisclosure in any way whatsoever.

Embodiments of this invention encompass methods which include applyingone or more metallic coating layer(s) including a metal, or including ametal matrix composite, or including both, to a substrate comprisingpyrolytic graphite. The microstructure of the metal of the metalliccoating layer may be amorphous, fine-grained metal, or a combinationthereof. As used herein, a “fine-grained metal” is metal having anaverage grain size between 1 and 5,000 nm. As used herein, the term“metal matrix composite” (MMC) is defined as particulate matter embeddedin a fine-grained and/or amorphous metal matrix (metal having an averagegrain size between 1 and 5,000 nm). The metallic coating layers have aroom temperature coefficient of linear thermal expansion (CLTE) in alldirections of less than 25×10⁻⁶ K⁻¹, for example, in the range between5.0×10⁻⁶ K⁻¹ and 25×10⁻⁶ K⁻¹. Embodiments of the invention alsoencompass the coated pyrolytic graphite articles, and specifically, heatspreaders.

The coatings comprising the fine grained metals, amorphous metals, orboth, and methods of applying them are described in U.S. PatentApplication Publication No. 2010/0028714, published Feb. 4, 2010, andU.S. Pat. No. 8,394,507, issued on Mar. 12, 2013. Such coatings areavailable as Nanovate™ coatings from Integran Technologies, Inc.,Toronto, Canada. In a preferred embodiment, the coating is a Nanovate™N2040 coating, a high strength, low coefficient of thermal expansionnanostructured Nickel-Iron coating, from Integran Technologies, Inc.,Toronto, Canada.

The application of the Nanovate™ N2040 coating, a high strength, lowcoefficient of thermal expansion nanostructured Nickel-Iron coating,from Integran Technologies, Inc., Toronto, Canada to a substrate ofpyrolytic graphite, specifically, PYROID® HT pyrolytic graphite, led toan increase of approximately 10% in the thermal conductivity of thesample. In all previous work, coating the pyrolytic graphite led to adecrease in thermal conductivity due to the increased thermal resistanceof the coating. In addition, the Nanovate™ N2040 coating increased themechanical properties, such as but without limitation, the flexuralstrength of the sample.

MMCs can be produced e.g. in the case of using an electroplating processby suspending particles in a suitable plating bath and incorporatingparticulate matter into the electrodeposit by inclusion or e.g. in thecase of cold spraying by adding non-deformable particulates to thepowder feed. Other methods of producing the metallic coating layersinclude DC or pulse electrodeposition, electroless deposition, physicalvapor deposition (PVD), chemical vapor deposition (CVD), and gascondensation or the like. Some exemplary methods include those describedin the following: U.S. Patent Application Publication No. 2005/0205425A1, published on Sep. 22, 2005; U.S. Pat. No. 7,387,578, issued on Jun.17, 2008; and DE 10,288,323.

Solid particulate materials that may be used in forming the MCCs includemetals (Ag, Al, Cu, In, Mg, Si, Sn, Pt, Ti, V, W, Zn); metal oxides(Ag₂O, Al₂O₃, SiO₂, SnO₂, TiO₂, ZnO); carbides of B, Cr, Bi, Si, W;carbon (carbon nanotubes, diamond, graphite, graphite fibers); glass;polymer materials (polytetrafluoroethylene, polyvinyl chloride,polyethylene, polypropylene, acrylonitrile-butadiene-styrene, and epoxyresins); and self-lubricating materials such as, but without limitation,MoS₂. The solid particulates may be up to 95% by volume of the coating,preferably, 1% to 95% by volume, more preferably 5% to 75% by volume,and even more preferably from 10% to 50% by volume.

Alloying additions may be used in the metallic coating layers and aredescribed in U.S. Patent Application Publication No. 2010/0028714, andU.S. Pat. No. 8,394,507, issued on Mar. 12, 2013.

There may be one or more intermediate coating layers between thesubstrate surface and the metallic coating layer(s). The intermediatecoating layer(s) may include, but are not limited to, a metal, apolymer, or both a metal and a polymer. Materials used in intermediatelayers are described in U.S. Pat. No. 8,394,507, and U.S. PatentApplication Publication No. 2010/0028714.

The surface of the substrate may be pre-treated by suitably rougheningor texturing at least one of the surfaces to be mated to form specificsurface morphologies, termed “anchoring structures” or “anchoring sites”as described in U.S. Pat. No. 8,394,507.

With respect to the substrates used, U.S. Pat. No. 8,394,507 discussespolymeric or polymer composites as substrates, but carbon substrates arenot disclosed. U.S. Patent Application Publication No. 2010/0028714discloses substrates of “carbon based materials selected from the groupof graphite, graphite fibers and carbon nanotubes.”

Graphite is made up of layer planes of hexagonal arrays or networks ofcarbon atoms. These layer planes of hexagonal arranged carbon atoms aresubstantially flat and are oriented so as to be substantially paralleland equidistant to one another. The substantially flat parallel layersof carbon atoms are referred to as basal planes and are linked or bondedtogether in groups arranged in crystallites. Conventional orelectrolytic graphite has a random order to the crystallites. Highlyordered graphite has a high degree of preferred crystallite orientation.As seen in FIG. 1, the graphite sheet 2 has hexagonal covalent bonds ina stacked crystal structure, and the graphite layers of each graphitesheet 2 are connected by van der Waals forces. The graphite sheet 2 hasa thermal conductivity in the X-Y plane of the graphite sheet 2 of avalue greater than in the thickness direction, i.e. the Z direction.Another way of characterizing graphite is as having two principal axes,the “c” axis or direction which is generally identified as the axis ordirection perpendicular to the carbon layers and the “a” axes ordirections parallel to the carbon layers and transverse to the c axes.This alternative nomenclature is also shown in FIG. 1. The “c” axis isequivalent to the Z direction, and the two “a” axes are equivalent tothe X-Y plane. As used herein with reference to the axes of a graphitesheet, the term “XY” will be used interchangeably with “a” and “a-a,”and the term “Z” will be used interchangeably with “c.”

Graphite materials that exhibit a high degree of orientation includenatural graphite and synthetic or pyrolytic graphite. Natural graphiteis commercially available in the form of flakes (platelets) or as apowder. Pyrolytic graphite is produced by the pyrolysis of acarbonaceous gas on a suitable substrate at elevated temperature.Briefly, the pyrolytic deposition process may be carried out in a heatedfurnace and at a suitable pressure, wherein a hydrocarbon gas such asmethane, natural gas, acetylene etc. is introduced into the heatedfurnace and is thermally decomposed at the surface of a substrate ofsuitable composition such as graphite having any desirable shape. Thesubstrate may be removed or separated from the pyrolytic graphite. Thepyrolytic graphite may then be further subjected to thermal annealing athigh temperatures to form a highly oriented pyrolytic graphite commonlyreferred to as HOPG.

For use in heat spreaders, it is preferable to use highly orientedpyrolytic graphite having thermal conductivities more than 1,500 W/mdegree K and a suitable example for use in particular is brand namePYROID® HT made by MINTEQ International Inc. in New York, N.Y.Generally, thermal conductivity is caused by the free electrons and thelattice vibration. The high thermal conductivity (1000-2000 W/m degreeK) of diamond is caused by lattice vibration, while the thermalconductivity of the extremely anisotropic HT graphite is equal to orless than diamond due to both free electron and the lattice vibration.

However, PYROID® HT pyrolytic graphite has many useful characteristics,such as the following: density 2.22 g/cc, tensile strength 28900 kPa (XYdirection), elastic modulus 50 GPa (XY direction), flexural modulus33200 MPa (XY direction), coefficient of thermal expansion0.6×10⁻⁶/degrees Celsius (XY direction), 25×10⁻⁶/degrees Celsius (Zdirection), thermal conductivity 1,700 Watts/m degree K (XY direction),7 Watts/in degree K (Z direction), 5.0×10⁻⁴ electric specific resistanceΩcm (XY direction), 0.6 Ωcm (Z direction), oxidation threshold 650degrees Celsius (XY direction), and permeability 10⁻⁶ mmHg.

The thermal conductivity of PYROID® HT pyrolytic graphite in the XYdirection compared with other materials thermal conductivity isextremely high, for example about 6 times the values of aluminum nitride(A1N) and beryllia (BeO), and about 4 times the value of the overallthermal diffusion of the material copper (Cu) in particular.

PYROID® HT pyrolytic graphite is produced by the CVD method as shown inFIG. 2. In chamber 20 under vacuum by a vacuum pump 21, hydrocarbon gassupplied from cylinder 22 as raw material gas is decomposed by the gasbeing heated to more than 2,000 degrees Celsius by heater 23, and whileminute carbon nucleus C which deposit and crystallize on substrate 24,stack and deposit in stratified formation, and PYROID® HT pyrolyticgraphite is produced. PYROID® HT pyrolytic graphite is available inthicknesses of from 0.25 mm to 20 mm, and can be produce as a board of avariety of sizes as large as 300 mm square shaped structure bycontrolling stacking and deposit time.

MINTEQ International Inc. in New York, N.Y. also makes PYROID® SN(substrate nucleated) and PYROID® CN (continuously nucleated) grades ofpyrolytic graphite also produced by the CVD process. These have lowerthermal conductivity than the PYROID® HT pyrolytic graphite.

Embodiments of the invention also encompass the coated pyrolyticgraphite articles. A specific use of the coated pyrolytic graphite is ina heat spreader. In preferred embodiments, PYROID® HT pyrolytic graphiteis used although other grades of PYROID® graphite, or other grades ofpyrolytic graphite may be used. In these embodiments, the heat spreaderis coated on all exterior surfaces, or substantially all exteriorsurfaces, with one or more metallic coating layers, and optionallyincluding one or more intermediate layers. The coating encases orencapsulates or essentially encases or encapsulates the heater spreader.Examples of heat spreaders that may be coated include any of thosedescribed in U.S. Pat. Nos. 8,085,531, 7,859,848, 7,808,787, and8,059,408. In preferred embodiments, the coating includes a Nickel-Ironalloy as a fine grained metal, amorphous metal, or combination thereof,optionally including a solid particulate, preferably a solid particulatethat is a polymer material. In preferred embodiments, the fine-grainedmetal, if present, is of a grain size of 2 nm to 5000 nm. In preferredembodiments, the metallic layer coating thickness is 10 to 500 μm.

In a preferred embodiment, the substrate is PYROID® HT pyrolyticgraphite, which is used as a heat spreader, coated on all surfaces oressentially all surfaces, with a 25 to 50 μm Nanovate™ N2040 coating, ahigh strength, low coefficient of thermal expansion nanostructuredNickel-Iron coating, from Integran Technologies, Inc., Toronto, Canada,and method of coating PYROID® HT pyrolytic graphite on all surfaces oressentially all surfaces with a 25 to 50 μm Nanovate™ N2040 coating.

EXAMPLES

The examples presented in this section are provided by way ofillustration of the current invention only and are not intended nor arethey to be construed as limiting the scope of this invention in anymanner whatsoever.

Example 1

Ten samples of PYROID® HT pyrolytic graphite were tested for thermalconductivity using ASTM E1461 Flash Method for Thermal Conductivitydetermination. In Table 1, for the first five samples, the thermalconductivity was measured in the XY orientation, and for the second fivesamples, the thermal conductivity was measured in the Z direction. Asshown in Table 1, the thermal conductivity, A in W/m-K, ranges from 1567to 1737 in the XY direction.

TABLE 1 ASTM E1461 Flash Method Thermal Conductivity Results thicknessbulk specific Δx @ density temperature heat diffusivity conductivity 25°C. ρ @ 25° C. T c_(p) α λ Sample (mm) (g/cm³) (° C.) (J/g-K) (mm²/s)(W/m-K) Pyroid-HT FAOBond 3.022 2.26 25 0.761 1010 1737 Lot# 11028-FAOPyroid-HT 2.970 2.24 25 0.772 967 1672 Lot# 12172 Plate 2C Pyroid-HT CN3.003 2.23 25 0.767 916 1567 Lot# 12172 Plate 9C Pyroid-HT 2.940 2.22 250.770 930 1590 Lot# 12172 Plate 10C Pyroid-HT 3.011 2.25 25 0.777 9751705 Lot# 12172 Plate 17C Pyroid-HT 3.208 2.30 25 0.846 24.6 47.9 Lot#10062-8805- Copper Plate 5A Pyroid-HT 3.180 2.31 25 0.882 23.4 47.7 Lot#12172-CN-8805- Copper Plate 9C Pyroid-HT 3.146 2.31 25 0.807 22.1 41.2Lot# 12172-8805- Copper Plate 10C Pyroid-HT 3.101 2.32 25 0.838 27.252.9 Lot# 12172-CN-VHB- Copper Plate 9C Pyroid-HT 3.027 2.30 25 0.81325.6 47.9 Lot# 12172-VHB- Copper Plate 10C

Example 2

Five samples of PYROID® HT pyrolytic graphite were tested for thermalconductivity using ASTM E1461 Flash Method for Thermal Conductivitydetermination. Samples #1-#3 labeled UA1051, UA1052, and UA1053 werecoated with a Nanovate™ Nickel-Iron alloy coating of coating thicknessesof 25 μm, 50 μm, and 50 μm, respectively. Samples #4 and #5 wereuncoated. The thermal conductivity of samples #1 and #2 was determinedin the XY direction. For samples #3-#5, the thermal conductivity wasdetermined in the Z direction. As shown in Table 2, the λ in W/m-K foreach of the two coated samples measured in the XY direction, samples #1and #2, was higher than any of the 5 uncoated samples measured inExample 1. In addition, the thermal conductivity in the Z direction washigher for coated sample #3 as compared to uncoated samples #4 and #5.

TABLE 2 ASTM E1461 Flash Method Thermal Conductivity Results Thicknessbulk specific Δx @ density temperature heat diffusivity conductivity 25°C. ρ @ 25° C. T c_(p) α λ Sample (mm) (g/cm³) (° C.) (J/g-K) (mm²/s)(W/m-K) UA1051 2.859 2.42 25 0.743 1082 1946 (#1) UA1052 2.895 2.47 250.720 982 1746 (#2) UA1053 2.905 2.42 25 0.742 5.47 9.82 (#3) 110282.976 2.24 25 0.771 4.40 7.60 (#4) 12172 2.995 2.24 25 0.833 4.32 8.06(#5)

Example 3

The flexure extension in the XY direction of 10 uncoated PYROID® HTpyrolytic graphite samples of 0.0625 inches in thickness and 0.5625inches in width and 0.90 inches in length at a temperature of 73° F. anda relative humidity of 50% was determined using the ASTM D790 testingprocedure. The results of 10 samples are shown in Table 3:

TABLE 3 Flexure stress at Load at Flex Yield Flex Yield Maximum MaximumPoint Point Calculations Yield Strain Calculations (psi) (%) (lb_(f)) 14891.09228 5.13 −9.55 2 5061.94668 5.09 −9.89 3 5132.65699 5.14 −10.02 44907.34853 0.41 −9.58 5 5340.14713 0.43 −10.43 6 5490.64692 0.42 −10.727 5059.92494 1.32 −9.88 8 5007.05097 1.24 −9.78 9 4720.94366 1.21 −9.2210 5369.86506 1.26 −10.49 Mean 5098.16242 2.16 −9.96 Standard 240.432572.07130 0.46959 Deviation

Example 4

The flexure extension in the Z direction of 4 uncoated PYROID® HTpyrolytic graphite samples of 0.0625 inches in thickness and 0.5625inches in width and 0.90 inches in length at a temperature of 73° F. anda relative humidity of 50% was determined using the ASTM D790 testingprocedure. The results of 4 samples are shown in Table 4:

TABLE 4 Flexure stress at Load at Flex Yield Flex Yield Maximum MaximumPoint Point Calculations Yield Strain Calculations (psi) (%) (lb_(f)) 17318.15204 0.79 −14.29 2 7535.14671 0.71 −14.72 3 10004.47820 −0.04−19.54 4 9512.44969 0.40 −18.58 Mean 8592.55666 0.47 −16.78 Standard1364.05628 0.37846 2.66417 Deviation

Example 5

The flexure extension in the Z direction of 4 coated PYROID® HTpyrolytic graphite samples of 0.0625 inches in thickness and 0.5625inches in width and 0.90 inches in length at a temperature of 73° F. anda relative humidity of 50% was determined using the ASTM D790 testingprocedure. Sample #1 was coated with a Nanovate™ Nickel-Cobalt alloycoating of 25 micron in thickness. Sample #2 was coated with a Nanovate™Nickel-Iron alloy coating of 25 micron in thickness. Sample #3 wascoated with a Nanovate™ Nickel-Cobalt alloy coating of 50 micron inthickness. Sample #4 was coated with a Nanovate™ Nickel-Iron alloycoating of 50 micron in thickness. The Nanovate™ coatings were providedby and applied by Integran Technologies, Inc. The results for the 4samples are shown in Table 5:

TABLE 5 Flexure stress at Load at Flex Yield Flex Yield Maximum MaximumPoint Point Calculations Yield Strain Calculations (psi) (%) (lb_(f)) 114700.55896 0.59 −28.71 2 20956.63154 3.00 −40.93 3 37968.68219 1.57−74.16 4 59287.40545 4.68 −115.80 Mean 33228.31954 2.46 −64.90 Standard19961.79046 1.78007 38.98787 DeviationAs seen in Table 5, the flexture stress was higher for each four of thesamples in Table 5 as compared to the samples shown in Table 4. Theyield strain was higher for all samples in Table 5 except sample #1.

Accordingly, it is understood that the above description of the presentinvention is susceptible to considerable modifications, changes andadaptations by those skilled in the art, and that such modifications,changes and adaptations are intended to be considered within the scopeof the present invention, which is set forth by the appended claims.

What is claimed is:
 1. A method: disposing a metallic coating layercomprising a metal over at least a portion of a surface of a pyrolyticgraphite substrate, the metal comprising Nickel, Iron, a Nickel-IronAlloy, or any combination thereof, and the grains of the metal being of1 nm to 10000 nm in size, the metal being amorphous, or both.
 2. Themethod of claim 1, wherein the pyrolytic graphite is highly orientedpyrolytic graphite, chemical vapor deposition deposited pyrolyticgraphite, or a combination thereof.
 3. The method of claim 1, whereinthe coating is a Nanovate™ N2040 coating.
 4. The method of claim 1,wherein the metal grain size is from 2 nm to 5000 nm.
 5. The method ofclaim 1, wherein the coating comprises an alloying addition.
 6. Themethod of claim 5, wherein the alloying addition is selected from thegroup consisting of B, C, H, O, P, S, and combinations thereof.
 7. Themethod of claim 1, wherein the coating comprises solid particulate ofmetals; metal oxides; carbides of B, Cr, Bi, Si, W, or a combinationthereof; carbon; glass; polymer materials; MoS₂, or any combinationthereof.
 8. The method of claim 7, wherein the coating comprises up to95% by volume solid particulates.
 9. The method of claim 1, wherein themetallic layer coating thickness is 10 μm to 50 mm.
 10. The method ofclaim 1, wherein one or more intermediate coating layers are appliedbefore the application of the metallic coating layer.
 11. The method ofclaim 10, wherein the intermediate coating layer comprises a metal, apolymer, or both a metal and a polymer.
 12. The method of claim 10,wherein the intermediate coating layer thickness is less than themetallic coating layer thickness.
 13. The method of claim 1, wherein themetallic coating layer covers all of the exterior surface of thesubstrate.
 14. The method of claim 1, wherein the metallic coating layercovers only a portion of the exterior surface of the substrate.
 15. Themethod of claim 1, wherein the substrate coated with the metalliccoating layer exhibits a thermal conductivity not less than the uncoatedsubstrate.
 16. The method of claim 1, wherein the substrate coated withthe metallic coating layer exhibits a thermal conductivity of about 105%of the thermal conductivity of the uncoated substrate, or of not lessthan 105% of uncoated substrate and also not more than 250% of theuncoated substrate.
 17. The method of claim 1, wherein the substratecoated with the metallic coating layer exhibits a thermal conductivityof about 110% of the thermal conductivity of the uncoated substrate, orof not less than 110% of uncoated substrate and also not more than 250%of the uncoated substrate.
 18. The method of claim 1, wherein thesubstrate coated with the metallic coating layer exhibits a thermalconductivity of about 115% of the thermal conductivity of the uncoatedsubstrate, or of not less than 115% of uncoated substrate and also notmore than 250% of the uncoated substrate.
 19. The method of claim 1,wherein the metallic coating layer has a room temperature coefficient oflinear thermal expansion in all directions of less than 25×10⁻⁶ K⁻¹. 20.An article comprising: a substrate of pyrolytic graphite; a metalliccoating layer comprising a metal deposited over at least a portion of asurface of the pyrolytic graphite substrate, the metal comprisingNickel, Iron, a Nickel-Iron Alloy, or any combination thereof, and thegrains of the metal being of 1 nm to 10000 nm in size, the metal beingamorphous, or both.